In the field of adhesive tape, Kraft tape, adhesive labels, adhesive seals, adhesive sheets and the like, release materials as represented by release paper are widely used. Such release materials can be produced using a method of directly coating a release agent solution consisting mainly of a solvent type, a non-solvent type or an emulsion type silicone resin onto a substrate such as paper. However, this method has the problem that the amount of silicone resin used is large, because in case that the substrate is permeable (for example, paper), the coating solution permeates into the substrate. To suppress permeation of the coating solution, it is currently mainstream to laminate the substrate with polyethylene, and coat a solvent-type silicone resin on top of that. However, in recent years the need to recycle paper for transformation into recycled paper has developed from the standpoint of resource and environmental concerns. To achieve that, it has become desirable to use a method that does not use a polyethylene laminate, which has low recoverability. Specifically, methods have been proposed in which in place of polyethylene a latex, such as SB latex or acrylic latex (JP-A-2001-2975), or a water-soluble resin, such as polyvinyl alcohol (JP-A-5-279995) is applied onto the substrate as an undercoating material, wherein the silicone resin is then applied. However, this method is not satisfactory in terms of performance and productivity. Another method that has been proposed directly applies a mixture of an aqueous emulsion and a silicone compound for hardening (JP-3-500060T); but this method has the drawbacks of insufficient releasability and increase of peel strength over time. Furthermore, for example, this method has the drawbacks that if the amount of silicone compound used is not increased, releasability is not exhibited.
Thus, the provision of a writable, printable release material has been desired wherein permanent ink, aqueous ink, an inkjet printer, a thermal-transfer printer and the like can be used on a release surface of Kraft tape, tack paper and the like. While methods that use a silicone resin as the release agent provide good releasability, their writing and printing properties are insufficient. On the other hand, while excellent writability and printability can be achieved when a non-silicone compound such as a compound containing long chain alkyl groups is used as the release agent, the releasability is insufficient. Until now there has not been a release material satisfying releasability together with writability and printability.
It is an object of the present invention to provide a release material, and a release agent used in the production thereof, which:
can be produced by directly coating onto a substrate without requiring the application of an undercoating material even when using a permeable substrate such as paper;
has excellent releasability even when the amount of silicone used is small;
has a low change in peel strength over time;
has a high residual adhesion ratio of an adhesive tape, seal and the like after release from a release material; and
has a surface which is writable or printable.